Properties of the heart muscle

With humans a heart muscle cell is on the average about 50 to 100 μm long and 10 to 25 μm broad. The left ventricle is the chamber from which blood is ejected into the body’s circulation.This must therefore provide a much higher pumping capacity than the right ventricle, which supplies blood exclusively to the lungs. For this reason, the heart muscle of the left ventricle is normally about twice as thick (1 cm) as that of the right ventricle, which is usually only about 0.5 cm thick. It is assumed that at the beginning of our life there are up to 6 billion cells in the muscles of the left ventricle. However, this number decreases steadily in the course of our lives, so that in older people it is probably only possible to detect a number of two to three billion cells.

Wall layers of the heart

The heart muscle is the middle of three layers that actually form the heart. On the very inside is the so-called endocardium, from which, for example, the heart valves also protrude. This is followed by the myocardium, i.e. the muscle layer, and on the very outside there is the epicardium. This is located at the pericardium, the pericardium that surrounds the entire heart and, with the help of the small amount of fluid it contains, functions as a kind of “shock absorber” and can protect the heart to a certain extent from external shocks and friction.

Diseases of the heart muscle

Diseases of the heart muscle (cardiomyopathy) can be mechanical, electrical or mixed. The term mechanical diseases of the heart muscle means a change in the size of the heart, the thickness of the walls and/or a change in the cavities (atria and ventricles), resulting in pumping disorders. In the case of electrical dysfunction, the transmission of electrical potentials is impaired so that the heart does not work physiologically.

As a rule, diseases of the heart muscle are often accompanied by an enlargement of the musculature. Several forms of myocardial diseases are subdivided. This is usually caused by high blood pressure in the body’s circulation.

In response to this, the left ventricle has to work harder to build up a pressure high enough to still be able to eject blood. As a result, more cells are formed and the heart muscle becomes thicker to be stronger. However, this only works up to a certain point, at which point the muscle is too thick to be supplied with sufficient blood.

Then the muscle can no longer work adequately and heart failure (cardiac insufficiency) occurs. In addition, the reduced supply of oxygen to certain muscle areas increases the risk of a heart attack. In this form of heart muscle disease, the chambers of the heart are enlarged without an increase in muscle size, with limited ejection capacity.

The heart muscles usually increase in size on the left side (sometimes also on the right side), which means that the heart is no longer able to pump enough blood from the chambers into the bloodstream. The chambers are worn out and there is not enough strength to eject the blood. In addition, the heart may experience a limited relaxation phase, whereby this phase is delayed, with the result that the heart becomes increasingly stiff, i.e. loses its elasticity.

This favors deposits of calcium in the vessels, which in turn can lead to severe secondary diseases. At the beginning of this disease, breathing difficulties may occur during exertion, later even without exertion. Rhythm disturbances are also likely to occur in the further course of the disease.

Thickening of the heart muscle
Erosion of the heart muscles (dilated cardiomyopathy)

This results in an increase of the heart muscles locally in the area of the ventricular septum in the left chamber. A distinction is made between two forms of the disease, in which the outflow path to the aorta, i.e. into the large body circulation, can be narrowed (severe course) or free (milder course). It is assumed that this type of heart muscle disease is congenital.

A high risk is suspected, especially for young male patients with a family history of sudden cardiac death, since this disease of the heart muscles is hereditary. This form of heart muscle disease is relatively rare and can be acquired and/or congenital in the course of life. How this form is acquired has not yet been clarified.

In this disease, the left ventricle is usually affected by a greatly reduced extensibility, but sometimes the right ventricle can also be affected. At the beginning of the disease, the atria enlarge and symptoms of heart failure such as shortness of breath occur. The innermost layer of the heart muscle thickens during the course of the disease and there is an increasing disturbance of the relaxation phase of the heart due to the reduced extensibility of the heart muscles.The cause of this disease of the heart musculature is still unclear.

Fatty tissue and connective tissue are deposited in the muscle tissue of the heart muscles. The right ventricle of the heart is affected. Since this form is usually accompanied by intact pumping performance, the disease can progress undetected and severe cardiac dysrhythmia can occur in the course of the disease.

The electrical potentials are not transmitted sufficiently or irregularly. The heart beats irregularly. Especially young men, especially athletes, are at risk of sudden cardiac death from this disease.

It is suspected that the cause is gene mutations in various structures that serve the communication between the heart muscle cells, as well as a defect in a receptor at the calcium storage of the heart. In this form of the disease there is an inflammation of the heart muscles. The inflammation can affect the heart muscle cells, the tissue between the layers of the heart muscle, as well as the heart vessels.

A distinction is made between chronic and acute inflammation, depending on its course. Inflammation can be caused by simple infections such as the flu virus or bacteria, toxic substances such as alcohol (very common) or heavy metals, fungi and parasites, drugs or autoimmune reactions. Often there is an unclear cause.

The extent of a heart muscle inflammation depends on the course of the disease. This can be without symptoms, but can also be associated with acute heart failure. Cardiac arrhythmia, chest pain, shortness of breath, as well as fatigue, general malaise and fever can be indications of a disease of the heart muscles, especially of inflammation.

Often the chronic form runs without symptoms, in contrast to the acute form. But even in the acute form, the course of the disease depends on the severity of the inflammation. This is a rare disease of the heart musculature that often affects women in the menopause.

It is usually triggered by strong emotional events and symptoms of an acute myocardial infarction occur. Chest pain, anxiety, sweating and severe paleness are possible symptoms. Due to the high level of stress, there is an increased release of adrenaline, which disrupts the function of heart muscle cells.

This form of the disease is a dilated cardiomyopathy caused by the high stress of pregnancy (see above). It can occur between the last trimester and five months after birth. The causes of this disease are not yet known.

Disease of the heart muscle due to an increase in muscle mass (hypertrophic cardiomyopathy)
Reduced elasticity of the chambers (restrictive cardiomyopathy)
Arrhythmia of the right ventricle (Arrhythmogenic right ventricular cardiomyopathy)
Heart muscle inflammation (myocarditis)
Stress cardiomyopathy (Tako Tsubo cardiomyopathy)
Cardiomyopathy before or after pregnancy (peripartal cardiomyopathy)

In order to strengthen the heart muscle, it is important not to cause overloading. In case of known cardiovascular diseases it is advisable to discuss the training units with a cardiologist or, if necessary, to carry them out under in-patient supervision. The heart muscles can be strengthened with light endurance sports and further training can be done by increasing the intensity, such as walking, inline skating, swimming, cycling or riding a recumbent bike.

In terms of time, a training session should last at least 20 minutes (15-17 minutes for beginners and re-starters). If you have a medium to good training level, the interval can be increased to 45 minutes. It is important to check your pulse while exercising, for example with a pulse watch or by palpating your pulse on your wrist with two fingers.

The resting pulse of a healthy person (untrained state) is about 60-70 heartbeats per minute (60-70/min). During endurance training, the pulse rate should generally not exceed 135/min. It is advisable to have your maximum heart rate determined under medical supervision.

In order to strengthen your heart, you should train in the optimal range. This is around 60%-75% of the maximum heart rate. Likewise, strong pressurized breathing such as during weight training with weights or strong resistance when cycling (only uphill) should be avoided. You should train 3-5 times per week, at the beginning 15-20 minutes at about 60% of the maximum heart rate. In order to strengthen the heart muscle, the training is gently increased to up to 75% during longer training sessions.